Nanostencil lithography is a substrate patterning method based on shadow mask evaporation. Typically, a thin silicon nitride membrane is used as a solid mask to transfer the pattern to the substrate during a single step of contact or close proximity evaporation.
Nanostencil lithography is simpler than conventional lithography processes since it requires no photoresist deposition, patterning and removal. Nanostencils are also potentially reusable many times to reproduce the same pattern in a number of substrates.
The thin silicon nitride membranes used for nanostencil lithography must be supported, and support is typically achieved by suspending the membrane in a thick silicon wafer structure. A pattern is then formed in the membrane using ion beam sputtering, reactive ion etching and electron beam lithography. This process affords the creation of pattern apertures of down to around 50 nm.
The minimum aperture size is generally proportional to the thickness of the silicon nitride membrane. In other words, for a 50 nm aperture the silicon nitride membrane should be around 50 nm thick. Silicon nitride curls and buckles under thermal stress. As a result, smaller apertures are more susceptible to curling and buckling during formation, and subsequently by material deposition during pattern transfer.
This curling and buckling blurs the aperture size and shape.
It is also difficult to control the distance between the stencil and substrate to which the pattern is being transferred. This lack of control can degrade transfer pattern resolution. While distance control is difficult, it is further hindered by curling and buckling of the apertures.
It is desirable, therefore, that a nanostencil and method for forming a nanostencil be provided that afford the creation of smaller apertures than those reproducibly achievable using prior art nanostencils, remedy one or more of the deficiencies of prior art nanostencils, or at least provide a useful alternative.